Water beetle (Hydrochus nitidicollis)
|Size||Adult length: 2.5 mm (2)|
Classified as Rare in Great Britain (3).
Hydrochus nitidicollis is a rare brassy, blackish coloured water beetle (1).
The British range of this species has always been restricted to Devon and Cornwall. Since 1970 it has been recorded in west Cornwall and on Falmouth and the Rivers Teign and Bovey in Devon. In mainland Europe this species has a western distribution. It is fairly widely recorded in the Iberian Peninsula and is found as far south as Morocco (3).
The larvae and adults of this species are aquatic, with a preference for clean running water. They can also been found in wet substrates both above and below the high water mark. This species is known as a river shingle beetle, as it is found in association with shingle and other exposed sediments at the margins of rivers (3).
Very little is known of the biology of this species. Adults and larvae are adapted to life in water, like other members of the genusHydrochus (2).
Like other river shingle beetles, the habitat of this species is likely to be damaged by a range of factors, including river straightening and dredging, control of the flow rate caused by damming or flood defence schemes, trampling by livestock, and the spread of the invasive plant Himalayan balsam (Impatiens glandulifera), which spreads very rapidly and competes aggressively with native species. Although there is no solid evidence to suggest that the range of this beetle has declined, a number of the sites where it has been recorded are threatened by development (3).
A number of beetles sharing this river shingle habitat have been highlighted as priority species under the UK Biodiversity Action Plan (UK BAP). A Group Action Plan has been produced to coordinate efforts to conserve these beetles. The Environment Agency, English Nature and the Countryside Council for Wales have joint-funded studies aiming to improve understanding of these species, in order to better guide their conservation (2).
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- Genus: a category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
- Larvae: stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.